REF: Stack allocate brng

[bashtage]

Use stack rather than heap allocation

[codecov]

Codecov Report

Merging #93 into 1.17.0 will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           1.17.0      #93      +/-   ##
==========================================
+ Coverage   93.47%   93.48%   +<.01%     
==========================================
  Files          25       25              
  Lines        7881     7845      -36     
  Branches      121      121              
==========================================
- Hits         7367     7334      -33     
+ Misses        494      491       -3     
  Partials       20       20

Impacted Files	Coverage Δ
randomgen/pcg64.pyx	82.92% <100%> (-0.41%)	⬇️
randomgen/xoshiro512starstar.pyx	79.16% <100%> (-0.64%)	⬇️
randomgen/pcg32.pyx	79.41% <100%> (-0.59%)	⬇️
randomgen/xoroshiro128.pyx	79.16% <100%> (-0.64%)	⬇️
randomgen/mt19937.pyx	81.08% <100%> (-0.5%)	⬇️
randomgen/xorshift1024.pyx	79.59% <100%> (-0.61%)	⬇️
randomgen/threefry.pyx	83.59% <100%> (-0.38%)	⬇️
randomgen/philox.pyx	83.84% <100%> (-0.37%)	⬇️
randomgen/dsfmt.pyx	84.12% <100%> (+1.55%)	⬆️
randomgen/xoshiro256starstar.pyx	80.58% <100%> (-0.55%)	⬇️
... and 1 more

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